1. Field of the Invention
This invention is related to fuels, especially hydrocarbon fuels, and lubricants, especially lubricating oils, and, more particularly, to a fuel or lubricant composition containing a class of anti-wear, anti-fatigue, and extreme pressure additives that are derived from 2-(S&N-mercaptobenzothiazole)succinic and methylene succinate esters. “S&N” refers to the sulfur and nitrogen bonding of the mercaptobenzothiazole to the maleate addition product. Alternatively, the nomenclature S(N)-mercaptobenzothiazole can be employed.
2. Description of Related Art
In developing lubricating oils, there have been many attempts to provide additives that impart anti-fatigue, anti-wear, and extreme pressure properties thereto. Zinc dihydrocarbyldithiophosphates (ZDDP) have been used in formulated oils as anti-wear additives for more than 50 years. However, zinc dihydrocarbyldithiophosphates give rise to ash, which contributes to particulate matter in automotive exhaust emissions, and regulatory agencies are seeking to reduce emissions of zinc into the environment. In addition, phosphorus, also a component of ZDDP, is suspected of limiting the service life of the catalytic converters that are used on cars to reduce pollution. It is important to limit the particulate matter and pollution formed during engine use for toxicological and environmental reasons, but it is also important to maintain undiminished the anti-wear properties of the lubricating oil.
In view of the aforementioned shortcomings of the known zinc and phosphorus-containing additives, efforts have been made to provide lubricating oil additives that contain neither zinc nor phosphorus or, at least, contain them in substantially reduced amounts. Illustrative of non-zinc, i.e., ashless, non-phosphorus-containing lubricating oil additives are the reaction products of 2,5-dimercapto-1,3,4-thiadiazoles and unsaturated mono-, di-, and tri-glycerides disclosed in U.S. Pat. No. 5,512,190 and the dialkyl dithiocarbamate-derived organic ethers of U.S. Pat. No. 5,514,189.
U.S. Pat. No. 5,512,190 discloses an additive that provides anti-wear properties to a lubricating oil. The additive is the reaction product of 2,5-dimercapto-1,3,4-thiadiazole and a mixture of unsaturated mono-, di-, and triglycerides. Also disclosed is a lubricating oil additive with anti-wear properties produced by reacting a mixture of unsaturated mono-, di-, and triglycerides with diethanolamine to provide an intermediate reaction product and reacting the intermediate reaction product with 2,5-dimercapto-1,3,4 thiadiazole.
U.S. Pat. No. 5,514,189 discloses that dialkyl dithiocarbamate-derived organic ethers have been found to be effective anti-wear/antioxidant additives for lubricants and fuels.
U.S. Pat. No. 3,293,181 discloses that zinc dialkyl dithiophosphates of improved thermal stability can be provided by the zinc salts of mixed dialkyl dithiophosphoric acids in which the alkyl groups are derived from a mixture of at least two different branched chain primary alcohols, one of the alcohols being isobutyl alcohol and the other containing at least six carbon atoms.
U.S. Pat. No. 3,396,109 discloses the preparation of phosphorus- and nitrogen-containing compositions by reacting a metal salt of a phosphinodithioic acid, especially a zinc salt of a diarylphosphinodithioic acid, with an amine, especially an aliphatic amine having from one to about forty carbon atoms. The compositions are said to be useful as additives for lubricating oils and automatic transmission fluids, in which they act as oxidation inhibitors and anti-wear agents. They are also said to afford synergistic oxidation inhibition properties when used with phenyl β-naphthyl amines.
U.S. Pat. No. 3,397,145 discloses an alkylthiophosphoric acid salt formed by the addition reaction thereof to a tertiary nitrogen atom of a condensation product containing said tertiary atom and comprising a polymeric reaction product.
U.S. Pat. No. 3,442,804 discloses a lubricating composition containing a small amount of a particularly defined zinc phosphorodithioate. The zinc phosphorodithioate is illustrated by that derived from dihydrocarbon phosphorodithioic acid in which the hydrocarbon radicals are primary alkyl radicals and consist of a mixture of lower molecular weight radicals (i.e., having less than 5 carbon atoms) and higher molecular weight radicals (i.e., having at least 5 carbon atoms). In the particularly defined zinc phosphorodithioate, the ratio of the lower molecular weight radicals to the higher molecular weight radicals, expressed on a molar basis, is with the range of 1:1 to 3:1.
U.S. Pat. No. 3,637,499 discloses lubricating oil compositions containing as anti-wear and detergent-inhibitor additives therein, an amine neutralized derivative of a dithiophosphoric acid prepared by reacting a long chain alkenyl-substituted C3-C8 monocarboxylic acid of 400-3,000 molecular weight with a primary or secondary hydrocarbylol amine, reacting the resultant amide with a phosphorus sulfide and neutralizing the resultant dithiophosphoric acid with a polyamino compound.
U.S. Pat. No. 4,696,763 discloses anticorrosive compositions that comprise: (A) an applicational medium selected from (a) surface coatings and (b) wholly or partly aqueous non-coating media, (B) as corrosion inhibitor, an effective corrosion-inhibiting amount of at least one aliphatic or cycloaliphatic mono-, di-, tri- or tetra-carboxylic acid ester or anhydride which is substituted in the aliphatic or cycloaliphatic residue by one or more groups having the formula
in which X is oxygen, sulphur or NH; and each R, independently, is hydrogen, alkyl, haloalkyl, alkoxy, alkylthio, alkylsulphonyl, cycloalkyl, phenyl, alkylphenyl, phenylalkyl, halogen, cyano, nitro, hydroxy, —COOH, —COOalkyl or a primary-, secondary- or tertiary amino- or carbamoyl group; or a non-toxic base addition salts of those components (B) which contain free carboxyl group.
U.S. Pat. Nos. 5,084,195 and 5,300,243 disclose N-acyl-thiourethane thioureas as anti-wear additives specified for lubricants or hydraulic fluids.
U.S. Pat. No. 5,498,809 discloses oil soluble copolymers derived from ethylene and 1-butene which have a number average molecular weight between about 1,500 and 7,500, at least about 30 percent of all polymer chains terminated with ethylvinylidene groups, and ethylene-derived content of not greater than about 50 weight percent, and which form solutions in mineral oil free of polymer aggregates, as determined by light scattering measurements. Lubricating oil additives, particularly dispersants, produced by the functionalization and derivatization of these copolymers are said to have enhanced performance (e.g., improved dispersancy and pour point) in lubricating oil compositions, attributable in part to the combination of properties characterizing the copolymers.
Japanese patent application JP1995268369A (Mar. 29, 1994) claims additives consisting of hydroxy polycarboxylic ester compounds., e.g., (R1—CO2)3C—OH, where R1 is alkyl group of 1-18 carbons. The lubricating oil compounds contain 0.1-40 wt. % of the hydroxy polycarboxylic ester additives. The additives are said to provide abrasion resistance to pure lubricating oils.
The disclosures of the foregoing references are incorporated herein by reference in their entirety.